Medial knee pain is a debilitating condition, often leading to significant disability in affected patients. It is particularly common in patients suffering from osteoarthritis (OA) of the knee.
There has been increasing recognition of a biomechanical basis for joint pathology in OA, and with this hope that a new generation of disease modifying therapies might follow. Of particular significance is the emergence of aberrant joint loading as driver of disease. During gait, the medial compartment of the tibiofemoral joint bears 2.5 times the load borne by the lateral compartment (Schipplein & Andriacchi J Orthop Res. 1991; 9(1):113-119), and is the usual site of manifestation of OA of the knee (Thomas et al. Radiology 1975; 116(3):585-594). Once OA is established, the external adduction moment (EAM) of the knee, a more readily determined correlate of the internally acting medial knee joint reaction force (JRF), has been shown to predict disease severity (Miyazaki et al. Ann Rheum Dis. 2002; 61(7); 617-622) and risk of progression (Sharma et al. Age 1998; 6(9):15), suggesting utility as a clinical marker for reduction.
Normal loading of the knee during gait and other activities of daily living involves significant tibial anterior shear and tibial internal rotation torque (Andersen & Dyhre-Poulsen Knee Surg Sports Traumatol Arthrosc. 1997; 5:145-149). The anterior cruciate ligament (ACL) is the primary restraint to anterior tibial translation (ATT) and a major secondary restraint to internal tibial rotation (Noyes et al. J Bone Joint Surg Am. 1983; 65(2):154-162) and thus ACL deficiency through sports trauma results in instability of the knee (Duthon et al. Knee Surg Sports Traumatol Arthrosc. 2006; 14(3):204-213).
Functional electrical stimulation (FES) is a non-invasive technology that induces muscle contraction via the application of a voltage gradient.